perl随笔-20070706.doc

perl随笔-20070706
变量
ID项目描述$ARGV传递进来的参数数组$0perl程序文件名$一般变量@数组%散列表$#var_name数组的最大下标STDIN,STDOUT,STDERR内置句柄，可以使用、关闭，重新open等$ARG
$_缺省的输入/循环变量
Thedefaultinputandpattern-searchingspace.Thefollowingpairsareequivalent:
while(<>){...}
while(defined($_=<>)){...}
/^Subject:/
$_=~/^Subject:/
tr/a-z/A-Z/
$_=~tr/a-z/A-Z/
chomp
chomp($_)@_@_containstheparameterspassedtothatsubroutine.$<digits>Containsthesubpatternfromthecorrespondingsetofcapturingparenthesesfromthelastpatternmatch,notcountingpatternsmatchedinnestedblocksthathavebeenexitedalready.(Mnemonic:like\digits.)Thesevariablesareallread-onlyanddynamicallyscopedtothecurrentBLOCK.$MATCH
$&local$_='abcdefghi';
/def/;
print"$`:$&:$'\n";#printsabc:def:ghi$PREMATCH
$`见上面例子$POSTMATCH
$'见上面例子
流程控制
ID项目描述if(!-f$ARGV[0])判断文件是否存在
正则表达式
OPERATORS
=~determinestowhichvariabletheregexisapplied.
Initsabsence,$_isused.
$var=~/foo/;

!~determinestowhichvariabletheregexisapplied,
andnegatestheresultofthematch;itreturns
falseifthematchsucceeds,andtrueifitfails.
$var!~/foo/;

m/pattern/igmsoxcsearchesastringforapatternmatch,
applyingthegivenoptions.
icase-Insensitive
gGlobal-alloccurrences
mMultilinemode-^and$matchinternallines
smatchasaSingleline-.matches\n
ocompilepatternOnce
xeXtendedlegibility-freewhitespaceandcomments
cdon'tresetposonfailedmatcheswhenusing/g
If'pattern'isanemptystring,thelastI<successfully>matched
regexisused.Delimitersotherthan'/'maybeusedforboththis
operatorandthefollowingones.

qr/pattern/imsoxletsyoustorearegexinavariable,
orpassonearound.Modifiersasform//andarestored
withintheregex.

s/pattern/replacement/igmsoxesubstitutesmatchesof
'pattern'with'replacement'.Modifiersasform//
withoneaddition:
eEvaluatereplacementasanexpression
'e'maybespecifiedmultipletimes.'replacement'isinterpreted
asadoublequotedstringunlessasingle-quote(')isthedelimiter.
?pattern?islikem/pattern/butmatchesonlyonce.Noalternate
delimiterscanbeused.MustberesetwithL<reset|HYPERLINK"file:///E:\\Perl\\html\\lib\\Pod\\perlfunc.html"perlfunc/reset>.

SYN