To be fair, Perl will usually just "do the right thing" for you with numbers inside strings.

But it can only read your mind so far. See:

    my $var1 = "12345";
    my $res1 = $var1 + 1;
    print "Result 1:  [$res1]\n";
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Results in:

    Result 1:  [12346]
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However:

    my $var2 = "1 2 3 4 5";
    my $res2 = $var2 + 1;
    print "Result 2:  [$res2]\n";
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Results in:

    Result 2:  [2]
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You see how Perl took the first number in the line and added 1 to it? But the rest of the line has been ignored, and thrown away.

If you want the rest of the numbers used, as noted throughout this thread, you have two choices:

1. Process them in a way that uses them, such as the use of split, or;
2. Put them on separate lines so file reading gets them separately.