http://www.perlmonks.org?node_id=85192


in reply to Re: How do I determine if a file was modified today?
in thread How do I determine if a file was modified today?

Nice and concice. If the poster meant "in the last 24 hours" to mean this calendar day, let's combine this concise answer with some of the others above:
if ( 1 > -M $file and (localtime((stat _)[9]))[3] == (localtime)[3] ) { # modified "in the last 24 hours" }
Beware of small, subtle bugs around Daylight Savings time.