use strict;
my $str = 'Sep04_17.00.37.tif Sep04_17.05.54.tif Sep04_17.08.41.tif
Sep04_17.02.02.tif Sep04_17.07.17.tif
';
my $regex = qr/[._]/p;
my $subst = '';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html