usually, ^ does mean at the beginning, but the [ and ] make a character class, and a ^ at the beginning of a character class means "not any of these".

Update:
Oddly enough, it doesn't explicitly say that in perlre. however, it does say
You can negate the [::] character classes by prefixing the class name with a '^'. This is a Perl extension.

In reply to Re^3: regex to remove all non a-z and spaces by mrborisguy
in thread regex to remove all non a-z and spaces by coldfingertips

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