Perl job interview questions (1)

1. How do you debug perl programs?
By turning on warnings and strictures, you can head off many problems before they get too big.
#!/usr/bin/perl
use strict;
use warnings;

2. How to open and read file in perl?
#!/usr/bin/perl
$LOGFILE = "input.txt";
open(LOGFILE) or die("Could not open log file.");
foreach $line (<LOGFILE>) {
print $line;
}
close(LOGFILE);


3. How to append a line at the top of a file?

#!/usr/bin/perl
$file = "input.txt";
open my $in, '<', $file or die "Can't read old file: $!";
open my $out, '>', "$file.new" or die "Can't write new file: $!";

print $out "# Add this line to the top\n"; 

while( <$in> )
{
print $out $_;
}
close $in;
close $out;

4. Check a string contains the word "World",
if($mystring =~ m/World/i) { print "Yes\n"; }

5. Substitute Hello with hello in a string.
#!/usr/bin/perl

$mystring = "Hello world!";
$mystring =~s/Hello/hello/;
print "$mystring\n";

6. Give an example of Perl subroutine.
#!/usr/bin/perl
 say_hello();

sub say_hello {
print "Hello, World!\n";
}

7. Print out the first element of an array.
#!/usr/bin/perl

@food  = ("apples", "pears", "eels");
print "$food[0]\n";

8. How to connect MySQL database using Perl?
#!/usr/bin/perl -w

use DBI;
## mysql user database name
$db ="mysql";
$user = "myname";
## mysql database password
$pass = "myPassword";

## user hostname
$host="localhost";


## SQL query
$query = "show tables";

$dbh = DBI->connect("DBI:mysql:$db:$host", $user, $pass);
$sqlQuery  = $dbh->prepare($query)
or die "Can't prepare $query: $dbh->errstr\n";

$sqlQuery->execute
or die "can't execute the query: $sqlQuery->errstr";

while (@row= $sqlQuery->fetchrow_array()) {
my $tables = $row[0];
print "$tables\n
";
}

$sqlQuery->finish;
exit(0);