my @aFruits = qw(apple bananna orange pear);

#declare a variable for the grep result
my @aSelected;

#define your condition
my $sCondition = q{/^b/ || /^p/};

#construct the grep command and evaluate it
my $sEval = "\@aSelected = grep($sCondition,\@aFruits)";
eval $sEval;

#see the results
print "selected fruits (eval): " . join(',', @aSelected) . "\n";