$s = 'variable chars anchor want this';;
$s = substr $s, index $s,'anchor';;
print $s;;
anchor want this

##</code><code>##

$s = 'variable chars anchor want this';;
$s =~ s[.+(?=anchor)][];;
print $s;;
anchor want this

##</code><code>##

cmpthese -1,{
    a=> q[$s='variable chars anchor want this';$s=~s[.+(?=anchor)][];],
    b=> q[$s='variable chars anchor want this';$s=substr $s, index $s,'anchor';]
};;
       Rate    a    b
a 1592446/s   -- -48%
b 3055291/s  92%   --