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Some great web pages to learn about Perl
Please comment if you know some more good ones.
Perl Basics
Perl Data Types
- Scalar -> $variable
- Array -> @array
- Associative Array (hash) -> %hash
- Combinations to make complex types easily (looks confusing but very powerful)
- Array of hashes $array[$i]->{$key}
- Hash of hashes $hash{$key}{$var}
- Multi-dimensional $var->{$key}->[0]->{$thing}
Use it!
Perl if statement
| Code Block |
|---|
|
use strict;
my $string = "this is a string";
if ( $string eq "string" ) {
print "$string is the same as \"string\"\n";
}
elsif ( $string =~ /string/ ) {
print "regex match $string has \"string\" in it\n";
}
elsif ( $string == 100 ) {
print "$string is the number 100\n";
}
else {
print "Else Nothing\n";
}
|
Perl Loops -> While
| Code Block |
|---|
while (condition) {
# do something
} |
Perl Loops -> for
| Code Block |
|---|
use strict;
my @array = (1, 2, 3, 4, 5, 6);
for ( my $i = 0; $i <= $#array; ++$i ) {
print “i=$array[$i]\n”;
} |
Perl Loops -> foreach
| Code Block |
|---|
use strict;
my @array = (1, 2, 3, 4, 5, 6);
foreach my $i ( @array ) {
print “i=$i\n”;
} |
Open a file and loop through
| Code Block |
|---|
use strict;
my $match = "blah";
my $file = "textfile.txt";
my $lines = 0;
open (DATA, $file) or die "ERROR with $file. $!";
while (<DATA>) {
chomp; # not necessary but gets rid of trailing spaces and newlines.
if ( $_ =~ /$match/) {
print "$lines: $_\n";
}
++$lines;
} |