Calling a shell script from a perl script

Hi,

I have one shel script which returns some value and I am calling this shell script from a perl script which needs the out put/return value of shell script.
But I don't know how to collect the output/return value of the shell script. Can any one give some idea on it?

For example:
The shell script a.sh

if [ $1 == 0 ]
then
return 0
else
retunr 1
fi

The perl script myperl.pl

$output = exec 'a.sh', '$ctr';
print $output;

When I run the perl script, It doesn't print anything. Even I tried by replacing return with exit in the shell script but no luck.

if [ $1 == 0 ]
then
     echo 'something'
     exit  0
else
    echo 'nothing'
fi
exit 1

and you execute a command line in perl with backtics: `cmd`, not single (forward) tics