I assume you're running this command from something like system() or the backtick operator, and if so you have a variety of choices for quoting your command line string. Check out the perlop|perlop manpage for further details about quoting in perl, and the quoting operators (you're positively spoilt for choice!).

# normal quoting
my $str = "isql [options] \"sp_start_job \@job_name='HHrun875'\"";
# non-interpolating quoting with q
my $str = q(isql [options] "sp_start_job @job_name='HHrun875'");
# interpolating quoting with qq
my $str = qq(isql [options] "sp_start_job \@job_name='HHrun875'");
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HTH

_________
broquaint