1. perldoc -f open
2. perldoc perlretut
3. use strict; use warnings

When you've read these, you'll pretty much have your answer.

But before you post a followup question, if any, On asking for help, How do I post a question effectively?, Markup in the Monastery and Super Search.

$ perl -n -e 'print if $_ eq "PEAR\n"' infile > outfile
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or

$ perl -n -e 'print if /^PEAR$/' infile > outfile
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The part in single quotes (the argument to the -e option) is the Perl script.  The -n option is equivalent to putting while (<>) { ... } around the code.

$_ eq "PEAR\n" or /^PEAR$/ tests if the current line (the default variable $_ here) holds your search string, where $_ =~ /.../ is implicitly assumed in the second case, i.e. a regular expression is by default matched against $_.

#!/usr/bin/perl

use strict;
use warnings;

while (<>) {
   chomp;
   ...;
   print ...;
}
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The program would be used as follows:

perl script.pl infile > outfile
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The line is present in variable $_. Check it and skip the print when it's not the value you want.

See also grep and grep alternatives.

word = ARGV.shift
File.open( ARGV.shift, 'r' ) do |in|
  File.open( ARGV.shift, 'w' ) do |out|
    in.each do |line|
      if line.chomp! == word
        out.puts line
      end
    end
  end
end
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Just do that in Perl and Bob's your paternal male sibling.

#!/usr/bin/perl -l
my $word = shift;
open my $in, '<', shift or die $!;
open my $out, '<', shift or die $!;
while (<$in>)
{
  print $out $_ if $_ eq $word;
}
close $in;
close $out;
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Howdy, Uncle Bob! Nice error checking!

---

print map{substr'hark, suPerJacent other l',$_,1}(11,7,6,16,5,1,15,18..23,8..10,24,17,0,12,13,3,14,2,4);

Ruby's File.open throws an exception which the default runtime behavior handles pretty well on its own (not to mention the error message includes the filename which yours doesn't), so yes.

$ ruby -e 'File.open( ARGV.shift, "r" ) { |f| puts f.readlines }' nott
+here
-e:1:in `initialize': No such file or directory - notthere (Errno::ENO
+ENT)
        from -e:1:in `open'
        from -e:1
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And if you're going to be that pedantic you might want to check for the error from print when you try and print to a filehandle you've opened for reading . . .

The cake is a lie.
The cake is a lie.
The cake is a lie.