# Basic syntax:
$your_string =~ s/regex pattern/text to substitute/;
# Where:
#	- regex pattern is the pattern to search for in $your_string
#	- text to substitute is the replacement text when the pattern is found
#	- add g after the last slash (/) to replace all matches for each line
# Example usage:
my $dna_sequence = "AACTAGCGGAATTCCGACCGT";
# substitute GAATTC with lowercase
$dna_sequence =~ s/GAATTC/gaattc/;
print "$dna_sequence\n";
--> AACTAGCGgaattcCGACCGT