It depends on your OS/shell. In unix-type shells, ! must be escaped because of its special meaning as a command history/substitution character. I just verified this on 3 shells: sh, bash and tcsh.

However, at a Windows DOS prompt, it is not necessary to escape the !.

In reply to Re^3: how to ignore regex in input to getopt::Long by toolic
in thread how to ignore regex in input to getopt::Long by Anonymous Monk

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