Here's another solution: 
my $input = '123+45';
my $output = '';
for ($input) {
   /\G ( \+ ) /xgc  && do { $output .= " $1 "; redo };
   /\G ( .  ) /xgcs && do { $output .= $1;     redo };
}
print("$output\n");

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<hint>If only Perl had a substitution operator, this parser wouldn't be needed...</hint>

In reply to Re^2: Reg exprs by ikegami
in thread Reg exprs by Anonymous Monk

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