$RETEZEC =~ s/TEXT1/TEXT2/; … zameni prvni vyskyt TEXT1 na radku textem TEXT2
$RETEZEC =~ s/TEXT1/TEXT2/g; … zameni kazdy vyskyt TEXT1 na radku textem TEXT2
$RETEZEC =~ s/TEXT1/TEXT2/gi; … zameni kazdy vyskyt text1 (nerozlisuje velka/mala pismena) na radku textem TEXT2
if( m/TEXT/ ) … Vyhledavani pomoci regularnich znaku

$ … konec retezce
. … any character except newline
a* … vyskyt znaku a 0 krat nebo vicekrat
+ … vyskyt znaku a 1 krat nebo vicekrat
? … match 0 or 1 times; or: shortest match
a? … zero or one a’s (i.e., optional a)
repetition? … same as repetition but the shortest match is taken

( ) … grouping; “storing”
[ ] … mnozina znaku
[abc] libovalny ze znaku: abc
[0-9] Libovlany ze znaky 0 az 9 podle asci tabulky
[\-] znak pomlcka
[\n] znak novy radek
[^abc] cokoliv, krome znaku abc
a{3} … znak a 3x po sobe
a{2,} … znak a alespon 2x po sobe
a{2,3} … znak a 2x az 3x
\ … quote or special

\t tabulator
\n novy radek
\r navrat na zacatek radku (CR)
\xhh znak pode sestnactkoveho kodu hh
\b “word” boundary
\B not a “word” boundary
\w slovni znak - ekvivalent [a-zA-Z_]
\W ne slovni znak
\s prazdny znak (mezera, tabulator, novy radek)
\S znak, jez neni prazdny znak
\d ciselny znak - ekvivalent [0-9]
\D Neciselny znak

abc 	abc (that exact character sequence, but anywhere in the string)
^abc 	abc at the beginning of the string
abc$ 	abc at the end of the string
a|b 	either of a and b
^abc|abc$ 	the string abc at the beginning or at the end of the string
ab{2,4}c 	an a followed by two, three or four b’s followed by a c
ab{2,}c 	an a followed by at least two b’s followed by a c
ab*c 	an a followed by any number (zero or more) of b’s followed by a c
ab+c 	an a followed by one or more b’s followed by a c
ab?c 	an a followed by an optional b followed by a c; that is, either abc or ac
a.c 	an a followed by any single character (not newline) followed by a c
a\.c 	a.c exactly
[abc] 	any one of a, b and c
[Aa]bc 	either of Abc and abc
[abc]+ 	any (nonempty) string of a’s, b’s and c’s (such as a, abba, acbabcacaa)
[^abc]+ 	any (nonempty) string which does not contain any of a, b and c (such as defg)
\d\d 	any two decimal digits, such as 42; same as \d{2}
\w+ 	a “word”: a nonempty sequence of alphanumeric characters and low lines (underscores), such as foo and 12bar8 and foo_1
100\s*mk 	the strings 100 and mk optionally separated by any amount of white space (spaces, tabs, newlines)
abc\b 	abc when followed by a word boundary (e.g. in abc! but not in abcd)
perl\B 	perl when not followed by a word boundary (e.g. in perlert but not in perl stuff)