#!/usr/bin/perl -w
    use strict;
    $/ = undef;
    my $text = <DATA>;
    $text =~ s/(BEGTITLE.*?)wirey(.*?ENDTITLE)/$1smooth$2/gsi;
    print $text;
    __DATA__
    BEGTITLE The wirey life of a wirey haired dog ENDTITLE
    BEGTXT blah blah blah ENDTXT
    BEGTITLE Grooming dogs ENDTITLE
    BEGTXT Grooming a wirey haired dog is ... ENDTXT
    BEGTITLE Last wirey haired dog story ENDTITLE
    BEGTXT we don't need no steenkin' wirey haired dogs here ENDTXT

# output is:

    BEGTITLE The smooth life of a wirey haired dog ENDTITLE
    BEGTXT blah blah blah ENDTXT
    BEGTITLE Grooming dogs ENDTITLE
    BEGTXT Grooming a smooth haired dog is ... ENDTXT
    BEGTITLE Last wirey haired dog story ENDTITLE
    BEGTXT we don't need no steenkin' wirey haired dogs here ENDTXT


##</code><code>##

    #!/usr/bin/perl -w
    use strict;
    while(<DATA>){
        s/wirey/smooth/gi if /BEGTITLE/ .. /ENDTITLE/;
        print;
    }
    __DATA__
    BEGTITLE The wirey life of 
    a wirey haired dog ENDTITLE
    BEGTXT blah 
    blah blah ENDTXT
    BEGTITLE Grooming dogs ENDTITLE
    BEGTXT Grooming a wirey haired dog is ... ENDTXT
    BEGTITLE Last wirey haired dog story ENDTITLE
    BEGTXT we don't need no steenkin' wirey haired dogs here ENDTXT

##</code><code>##

    BEGPUB Wirey Haired Dogs Life ENDPUB BEGTITLE My dog 
    has wirey hair ENDTITLE
    BEGTXT My 
    wirey hair dog...blah, blah. 
    ENDTXT

    or 

    BEGTITLE My dog 
    still has wirey 
    hair ENDTITLE BEGTXT more wirey
    haired dog stuff ENDTXT

##</code><code>##

    #!/usr/bin/perl -w
    use strict;
    $/ = undef;
    while(<DATA>){
        s{(BEGTITLE.*?ENDTITLE)}
          { my $rec = $1;
            $rec =~ s/wirey/smooth/ig;
            $rec;
          }gse;
        print;
    }
    __DATA__
    BEGTITLE The wirey life of a wirey haired dog ENDTITLE
    BEGTXT blah blah blah ENDTXT
    BEGTITLE Grooming dogs ENDTITLE
    BEGTXT Grooming a wirey haired dog is ... ENDTXT
    BEGTITLE Last wirey haired dog story ENDTITLE
    BEGTXT we don't need no steenkin' wirey haired dogs here ENDTXT
    BEGPUB Wirey Haired Dogs Life ENDPUB BEGTITLE My dog 
    has wirey hair ENDTITLE
    BEGTXT My 
    wirey hair dog...blah, blah. 
    ENDTXT
    BEGTITLE My dog 
    still has wirey 
    hair ENDTITLE BEGTXT more wirey
    haired dog stuff ENDTXT