Think about first letter and the later parts are some specific symbol ( .-).

8 digits or 10 digits

cleans up a semicolon delimited list (remove white spaces, multiple semicolons, semicolons at the beginning or the end)

validates any date in M-d-yyyy format from 1581-01-01 to 9999-12-31, allowed delimiters are "/", "." and "-"

validates any date in yyyy-M-d format from 1581-01-01 to 9999-12-31, allowed delimiters are "/", "." and "-"

validates any date in (d)d-(M)M-yyyy format from 1581-01-01 to 9999-12-31, allowed delimiters are "/", "." and "-"

this will match the frequently and rarely using musical chords in a sheet music

password 8-16 characters atleast 1 lowercase,1 upper case,1 Spl. char,1 digit

Should be able to match a dot-separated decimal number (C-style) Works with: integers floating-point scientific notation

This will find SSN in multiple forms in a document. Source for ED https://www.jscape.com/blog/bid/79591/exploring-regular-expressions-in-dlp