my ($nobrackets) = (qr/[^\{^\}]+/);
&replace(qr/\{$nobrackets\}/,'$1') #This line is changed below.

sub replace{
s/$_[1]/$_[2]/g
}

##</code><code>##

my ($nobrackets) = (qr/[^\{^\}]+/);
&replace(qr/\{$nobrackets\}/,"$1") #Using qq// instead of q//.

sub replace{
s/$_[1]/$_[2]/g
}

##</code><code>##

#!/usr/bin/perl
$_='{\selectlanguage{english}
\textcolor{black}{\ \ 10.\ \ Three resistors connected in series each
carry currents labeled }\textit{\textcolor{black}{I}}\textcolor{black}{\textsubscript{1}}\textcolor{black}{,
}\textit{\textcolor{black}{I}}\textcolor{black}{\textsubscript{2}}\textcolor{black}{and}\textit{\textcolor{black}{I}}\textcolor{black}{\textsubscript{3}}\textcolor{black}{.
Which of the following expresses the value of the total current
}\textit{\textcolor{black}{I}}\textit{\textcolor{black}{\textsubscript{T}}}\textcolor{black}{in the system made up of the three resistors in series?}}.';;
$nobrackets  = qr/[^\{}]+/;  
my $pass = 0;
while(++$pass <=2){
s/\\textsuperscript\{($nobrackets)\}/ startsuperscript $1 endsuperscript /g;
s/\\textsubscript\{($nobrackets)\}/ startsubscript $1 endsubscript/g;
s/\\textit\{($nobrackets)\}/ startitalic $1 enditalic/g;  
s/\\textcolor\{$nobrackets\}//g;
s/\{($nobrackets)\}/($1)/g;
 print "Pass $pass:\n\n". qq{$_}."\n\n\n";
}

##</code><code>##

Pass 1:

{\selectlanguage(english)
(\ \ 10.\ \ Three resistors connected in series each
carry currents labeled )\textit{(I)}( startsubscript 1 endsubscript)(,
)\textit{(I)}( startsubscript 2 endsubscript)(and)\textit{(I)}( startsubscript 3
 endsubscript)(.
Which of the following expresses the value of the total current
)\textit{(I)}\textit{( startsubscript T endsubscript)}(in the system made up of
the three resistors in series?)}.


Pass 2:

(\selectlanguage(english)
(\ \ 10.\ \ Three resistors connected in series each
carry currents labeled ) startitalic (I) enditalic( startsubscript 1 endsubscrip
t)(,
) startitalic (I) enditalic( startsubscript 2 endsubscript)(and) startitalic (I)
 enditalic( startsubscript 3 endsubscript)(.
Which of the following expresses the value of the total current
) startitalic (I) enditalic startitalic ( startsubscript T endsubscript) endital
ic(in the system made up of the three resistors in series?)).