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Real-world data — phone numbers, dates, emails, log entries, product codes — arrives inconsistently. Here are the regex patterns for the most common data cleaning tasks: phone normalisation, date standardisation, HTML stripping, whitespace cleaning, and log redaction.

Reversing Arabic text character-by-character produces nonsensical output — Arabic is stored in logical reading order and reversed by a rendering engine, so reversing code points produces different words backward, not mirrored text. Here's how Unicode's bidirectional algorithm assigns direction to each character, why emoji sequences need grapheme cluster reversal rather than code-point reversal, and how the Trojan Source vulnerability exploited RLO (Right-to-Left Override) control characters to hide malicious code in source file reviews.

Deduplication is a business logic decision masquerading as a technical one — "duplicate" means different things for contact lists (same email, different fields) vs URL lists (case sensitivity, trailing slashes) vs product catalogs (same SKU, different descriptions). Here's the exact vs near-duplicate distinction, normalization as the preprocessing step that determines deduplication quality, CRM merge strategies, and URL-specific case sensitivity rules.

"Lorem ipsum" isn't a real Latin phrase — it's literally the tail end of "dolorem ipsum" ("pain itself"), cut off mid-word from a genuine passage of Cicero's philosophy, then scrambled and partially invented over centuries of typesetting. Here's the actual source text, how a coherent philosophical passage became nonsense, and why the "fakeness" arguably works in its favor as placeholder text.

MySQL silently truncates strings that exceed VARCHAR column lengths — no error, just missing data. Here's database silent truncation, CSS text-overflow and multi-line clamping, the accessibility problem with truncated UI text, API response truncation flags, and the Windows 260-character path length problem.

Three-way merge — Git's algorithm for combining two branches — uses a third input (the common ancestor) to determine who changed what, enabling automatic combination when edits don't overlap. Here's why merge conflicts occur exactly where they do (both sides changed the same region), the diff3 conflict format that shows the base alongside ours/theirs, why "no merge conflicts" doesn't mean the code is correct (semantic conflicts), and why "ours" and "theirs" flip meaning between git merge and git rebase.

Lorem Ipsum's Latin word-length distribution is statistically different from English, which is why layouts that look balanced with placeholder can break with real copy. Here's the average word length across languages, why button and navigation placeholder text is particularly misleading, how Cicero's long-sentence rhetorical style differs from web copy, and when content-first design eliminates the placeholder problem entirely.

Zero-width spaces and zero-width non-joiners are used to watermark confidential documents — each recipient gets a unique binary pattern embedded invisibly, allowing leaks to be traced back to the specific recipient. Here's the full taxonomy of invisible Unicode characters (U+200B zero-width space, U+00A0 non-breaking space, directional controls), why Python's str.strip() doesn't remove non-breaking spaces, and how invisible characters are used to bypass content filters by breaking exact-match pattern recognition.

Legal document redlining, Git pull request review, Word's Track Changes, and AI writing assistants all use the same diff principle. Here's how each context uses comparison differently, why legal diff needs more than plain text comparison, and how AI tools use diff to show suggested edits.

sed's `s/old/new/g` fails when patterns contain forward slashes (like file paths) — but any character can be the delimiter: `s|/usr/local|/usr/share|g` works identically. Here's the complete sed substitution syntax including & for matched content and \1 capture groups, the -i in-place editing difference between GNU sed (Linux) and BSD sed (macOS), and why grep-first-then-sed is the workflow that prevents data loss.