Seconding hippo's comment, perhaps it helps to understand that

print "something";
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(which you are already using), is just an abbreviation for

print STDOUT "something";
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and instead of

        open ($fh, '>', $temporary_fileName) or die $!;
        `echo "... long string ..." > $temporary_fileName`;
        close ($fh);
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where open and close are effectively useless, you should use

        open ($fh, '>', $temporary_fileName) or die $!;
        print$fh "... long string ...";
        close ($fh);
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(I prefer to put the file handle after print without a space to help remembering there's no comma after the file handle)

If you feel adventurous, you might to look over Text::Table Tutorial, but that's an advanced topic, just to see what's possible.