if ( some condition ) {
  print "It's true\n";
} else {
  print "It's false\n";
}

##</code><code>##

if ( some condition ) {
  print "It's true\n";
} 
else {
  print "It's false\n";
}

##</code><code>##

if    ( Some condition 1 ) {
  print "First case\n";
} 
elsif ( Some condition 2) {
  print "Second case\n";
}
else {
  print "Default case\n";
}