comment on

Beware that this approach cannot discover the last defined match variable, since there may be gaps in the list: for example after "b" =~ /(a)?(b)/, $1 will not be defined even though $2 is.

Since there is no useful absolute limit on the highest numbered match variable you might need to check for, I wondered whether walking the symbol table might give a clue, but no such luck - the symbol table entries for *1 etc are created only if they are explicitly referenced in the code:

  "abcde" =~ /(.)(.)(.)(.)(.)/;
  my $var = $4;
  print join ', ', grep !/\D/, keys %::;
[download]

prints "0, 4".

Accordingly, I think it is not possible in pure perl to discover the highest numbered defined match variable using any perl before v5.6.0 (when @+ and friends were first introduced).

Hugo

In reply to Re: Re: Finding the right $<*digit*> capture variable by hv
in thread Finding the right $<*digit*> capture variable by diotalevi

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