undef $/; 
my $number = 42; 
#or $number = $ARGV[0] or whatever line number you were looking for
my $file = <FILE>;
my ($line, $name); 
# ($line) = $file =~ /$($number\s+.*)/m;
# would store the whole line 

($number, $name) = $file =~ /$($number)\s+(.*)/m;

# use the second form since you just want number and name
# and yes, you are overwriting the value of $number
# with itself all over again.  Use (undef, $name) = $file...
# if that makes you feel more comfortable.