Both BazB and metadoktor give good advice.

I had another thought. This may not be your problem but here it is anyway. When you capture the output of a command using backticks, only STDOUT is captured, not STDERR. In a CGI program, STDERR goes into the web server's errorlog. You can capture both STDOUT and STDERR (intermingled) in the same stream by appending '2>&1' to the command.

$encStr = `echo $plainStr | /usr/bin/gpg -ea --always-trust -r user\@d
+omain.com 2>&1`;
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dmm

If you GIVE a man a fish you feed him for a day
But, TEACH him to fish and you feed him for a lifetime