In such cases, one is tempted to write this:

$string = "johnq.smith1"; $string =~ /(\d+$)/ or die "no number"; $1++
+; print $string, $/; # WRONG
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That's however invalid, so let's do this:

$string = "johnq.smith1"; $string =~ /(\d+$)/ or die "no number"; matc
+h($string, 1)++; print $string, $/; 
sub match : lvalue { my $n = $_[1] || 0; substr $_[0], $-[$n], $+[$n] 
+- $-[$n]; }
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that doesn't have much advantage over a simple substitution of course.

One could even create a tied array for the modifiable versions of $1, $2, ...

{ package Matched; sub TIEARRAY { bless \my$x, $_[0]; } sub FETCH { my
+ $n = $_[1]; substr $_, $-[$n], $+[$n] - $-[$n]; } sub STORE { my $n 
+= $_[1]; substr($_, $-[$n], $+[$n] - $-[$n]) = $_[2]; } tie @~, Match
+ed::; } 
local $\ = $/; $_ = "johnq.smith1"; /(\d+$)/ or die "no number"; $~[1]
+++; print;
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