You could use a file test like -e in a while loop: 
my $output_file = "output_$input_file";
my $i = 1;
while (-e $output_file) {
    $output_file = "output_$input_file$i";
    $i++;
}

$abc_cmd = "abc.exe -i $input_file -o $output_file ";

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In reply to Re: incrementing the file by toolic
in thread incrementing the file by abcdefg

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