Debugging: Cron: % sign

Error message:

/bin/sh: -c: line 0: unexpected EOF while looking for matching `]'
/bin/sh: -c: line 1: syntax error: unexpected end of file

The source code:

*/10 * * * * perl -le 'sleep rand 60' && head -$[${RANDOM} % `wc -l < /Users/username/lines.txt` + 1] /Users/username/lines.txt | tail -1 | ruby /Users/username/tweet.rb

Crontab man page:

The entire command portion of the line, up to a newline or % character, will be executed by /bin/sh or by the shell specified in the SHELL variable of the cronfile. Percent-signs (%) in the command, unless escaped with backslash (\), will be changed into newline characters, and all data after the first % will be sent to the command as standard input.

Fixed source code:

*/10 * * * * perl -le 'sleep rand 60' && head -$[${RANDOM} \% `wc -l < /Users/username/lines.txt` + 1] /Users/username/lines.txt | tail -1 | ruby /Users/username/tweet.rb