Clearcase command line mkattr needs to wrap variable $bug_num between single quote + quote + $varible + quote + single quote, like this:
cleartool mkattr -replace BUGNUM '"$bug_num"' clearcase_file
How to make a call of the command cleartool mkattr in a Perl script in Unix env? Env is Unix AIX and ksh
As mentioned in this recent answer:
If you want to execute a system command and don't have to use any shell syntax like redirects, it's usually better and safer to use the list form of system:
system(
'cleartool', 'mkattr', '-replace', 'BUGNUM ',
qq{"$bug_num"}, qq{clearcase_file}
);
# or, if you really want to pass both types of quotes:
system(
'cleartool', 'mkattr', '-replace', 'BUGNUM ',
qq{'"$bug_num"'}, qq{clearcase_file}
);
Or:
system(qq{cleartool mkattr -replace BUGNUM '"$bug_num"' clearcase_file});