I sometimes want to match whitespace but not newline.
So far I've been resorting to
I am shocked that so many unnecessarily elaborate answers have been written. By far the cleanest way, which will work on version 10 and later of Perl 5, is to use the horizontal whitespace character class
\h. This will match just horizontal tab and space from the ASCII set, or any of these Unicode characters.
CHARACTER TABULATION SPACE NO-BREAK SPACE OGHAM SPACE MARK MONGOLIAN VOWEL SEPARATOR EN QUAD EM QUAD EN SPACE EM SPACE THREE-PER-EM SPACE FOUR-PER-EM SPACE SIX-PER-EM SPACE FIGURE SPACE PUNCTUATION SPACE THIN SPACE HAIR SPACE NARROW NO-BREAK SPACE MEDIUM MATHEMATICAL SPACE IDEOGRAPHIC SPACE