Hi,
if you were just after the first '99' in your string, just omit the 'g'-Modifier, otherwise use more groupings to do it: 
my $reg = '99';
my $replace = 'XX';

my $line = "0165451234599123459935589";
print $line, "\n";

$line =~ s/$reg/$replace/;
print $line, "\n";

$line = "0165451234599123459935589";
$line =~ s/(12345)($reg)(12345)/$1$replace$3/;

print $line, "\n";

[download]
prints 
0165451234599123459935589
01654512345XX123459935589
01654512345XX123459935589

[download]

Regards,
svenXY

In reply to Re: Specific substitution in regular expressions by svenXY
in thread Specific substitution in regular expressions by cstrong

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