my $str    = "ABXCDEFDGXTGRAAAAAA";
my $start  = 5;
my $char   = "X";
my $end    = index($str, $char, $start);
my $result = substr($str, $start, $end-$start);

print $result, "\n";
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What is so complicated/annoying about the code above? If you don't like it, merge lines 4 and 5 into one line - or move them to a sub...

HTH, Rata