Rephrasing what ikegami said already:
the output of `unix_tool file_name` is probably _empty_.
What if you run this very command in the shell?
What if you use the full path to unix_tool inside the backticks, if unix_tool isn't in the current directory?
Maybe these questions can help you in tracking the problem down.
Update: what if you dump out $var after filling it, like
print Dumper( $var );
Altough this sounds improbable, maybe you just falled over some bug, maybe one that appears only within your environment: what Perl do you use, on what OS?
Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
Read Where should I post X? if you're not absolutely sure you're posting in the right place.
Please read these before you post! —
Posts may use any of the Perl Monks Approved HTML tags:
You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
- a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
Link using PerlMonks shortcuts! What shortcuts can I use for linking?
See Writeup Formatting Tips and other pages linked from there for more info.
| & || & |
| < || < |
| > || > |
| [ || [ |
| ] || ] ||