if( grep $question eq $_, 'a', 'b' 'c' ) {
    # ...
}
[download]

Or, depending on what you're doing,

my %questions;
undef @questions{ 'a', 'b', 'c' };

# and then

if( exists $questions{ $question } ) {
    # ...
}
[download]

Update: s/==/eq/ per thor’s notice.

Makeshifts last the longest.