use strict;
my $str = 'interface gpon_olt-1/1/1 onu 1 type ZTE-OMC3 sn ZTEGC0CD5938
interface gpon_olt-1/1/1 onu 2 type ZTE-F612 sn ZTEGC8BF978F
interface gpon_olt-1/1/1 onu 3 type ZTE-OMC3 sn ZTEGC8653DA1
interface gpon_olt-1/1/1 onu 4 type ZTE-OMC3 sn ZTEGC4BC9D80
interface gpon_olt-1/1/1 onu 5 type ZTE-F670 sn ZTEGCE8DA5F5
interface gpon_olt-1/1/1 onu 7 type ZTE-F670 sn ZTEGC8509BBE
interface gpon_olt-1/1/1 onu 8 type ZTE-F670 sn ZTEGC8B65274';
my $regex = qr/\d+/\d+/\d+/mp;
my $subst = '\\1';
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