#!/usr/bin/perl -w
use strict;
use List::Util (qw/first/);            #a core function in all Perl's
use List::MoreUtils (qw/first_index/); #not core but a common module

#first{} stops at the first occurrence, slightly faster than grep{} 
#first_index() reports index of {block}

while (my $line = <DATA>)
{
  my @array = split /\s+/, $line;
  print "A One is in: $line" if (first {$_ == 1}@array);
  my $index = first_index{$_ == 1}@array;
  print "index of the One=\[$index\]\n" if $index >-1;
}

=output
A One is in: 5 10  14  16  17  20  25  26  38  1  42   47  54
index of the One=[9]
A One is in: 5 1
index of the One=[1]
A One is in: 1 2342
index of the One=[0]
=cut

__DATA__

5 10  14  16  17  20  25  26  38  1  42   47  54
5 10  14  16  17  20  25  26  38  42   47  54
5 1
4 10
1 2342
34 55