I know your title asks for a regex, but maybe split will do: 
use strict;
use warnings;

while (<DATA>) {
    chomp;
    my @parts = split /\./;
    pop @parts;
    my $file_no_ext = join '.', @parts;
    print "file_no_ext = $file_no_ext\n";
}

__DATA__
foo.bar.txt
goo.doc
boo.hoo.moo

[download]

prints: 

file_no_ext = foo.bar
file_no_ext = goo
file_no_ext = boo.hoo

[download]

In reply to Re: Regex To Remove File Extension (split) by toolic
in thread Regex To Remove File Extension by Anonymous Monk

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