$tmp =~s/TBGL_([a-z]+(\.[a-z]+)?)/$1_gl/i;

##</code><code>##

$tmp =~s/TBGL_([a-z]+)/$1_gl/i;

##</code><code>##

#!/usr/bin/perl

use strict;

my @lines = (
'title>TBGL_SetMaterialDiffuse</title',
'Heading1">TBGL_SetMaterialDiffuse</span',
'href="tbgl_SetMaterialDiffuse.htm">',
'">tbgl_SetMaterialDiffuse</',
'f_Code_Keyword">TBGL_DeleteMaterial</span'
);

foreach my $tmp (@lines) {
        print "$tmp\n";
        #$tmp =~s/TBGL_([a-z]+(\.[a-z]+)?)/$1_gl/i; #case 1
        $tmp =~s/TBGL_([a-z]+)/$1_gl/i; #case 2
        print "$tmp\n\n";
}