Your problem is that your regex effectively boils down to /\d{12}/ ignoring the substitution and variable capture, so it will only match a 12 digit number.
You actually need to match the _ and : characters.
What you want would be something like.
my $file = "textfile.020701_00:08";
my $time = substr($file, 9,12);
$time =~ s/(\d{6})_(\d{2}):(\d{2})/"$1$2$3.monday"/;
print "TIME: $time";

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In reply to Re: extract date from filename - need help by Lachesis
in thread extract date from filename - need help by star7

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