#!/usr/bin/perl -w
use strict;

my $dat = 'size="10">20iliX 234bvc 234yyyyy size="10">35iliX';

$dat =~ s/size="10">(\d{1,2})iliX/size="10" text-anchor="end">$1iliX/g;
print $dat;
#size="10" text-anchor="end">20iliX 234bvc 234yyyyy size="10" text-anchor="end">35iliX